This application proposes to study pigeons' choice for variable food magnitude in order to understand how food value is established and how variable information about food magnitude is processed and acted upon.The first two experiments are directed at understanding the psychophysical scale that underlies food information processing. Variable food sources versus fixed food sources using the time-left paradigm will be investigated. Variability in food magnitude will be introduced by manipulating feeder access duration. The results will be analyzed in light of several theoretical accounts. Experiment 3 will test the generality of the findings from the time-left paradigm to another choice procedure, a titration design. Experiments 4 and 5 will study the effects of differing probability structures for the variable option. Three different lines of research are proposed for the final stages of the project. The first one will analyze food value attribution in a situation where food consist of discrete items, rather than a continuous feeder access. The second line will investigate which kind of currencies animals use to value food. Experiments using pellets will be conducted with different energetic content as different reward magnitudes, in order to separate temporal and quantitative features of food reward. The third and last line will extend the findings of experiments 2 and 4 to a situation where there are variable options with complex probability distributions.